Fix <sys/select.h> for LP64, clean up <time.h>.

The 64-bit uapi headers don't define FD_CLR and friends, so this
patch updates libc/kernel/common/linux/time.h after the change
b934bbec145e9e084bf48149a3a94ae3dd132157 in external/kernel-headers,
then fixes <sys/select.h> to work in this new world, and removes
some now-unnecessary duplication from <time.h> (with other cruft
cleaned up while I'm here).

Change-Id: Ifd26f901b4d200c65065b3e6ef1b74055127e052